JPS6016748B2 - Manufacturing method of semiconductor device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a Ryozo method for a semiconductor device,
Particularly preferably, the present invention relates to a method of fabricating electrode wiring of a semiconductor device having a shallow junction.

Aluminum has generally been used as the electrode material for semiconductor devices, but since aluminum undergoes alloy decomposition with semiconductor materials at relatively low temperatures, it is often used in ultra-high frequency boosting transistors and ultra-high speed switch transistors. In the case of a semiconductor device having an extremely shallow junction such as the above, there is a drawback that the reaction region easily reaches the junction and destroys the junction.

For this reason, conventional semiconductor devices using aluminum electrodes have been extremely unstable thermally. An object of the present invention is to provide a new fabrication method that allows a highly reliable semiconductor device to be easily obtained. That is, a feature of the present invention is that a first metal layer is formed on a semiconductor substrate having a silicon oxide film on a predetermined surface, a second metal layer is formed on the first metal layer, and a second metal layer is formed on the first metal layer. When selectively converting a laminated metal layer body in which a third metal layer is formed on a metal layer into an electrically insulating material, the second metal layer and the third metal layer have different conversion characteristics. , thereby first selectively converting the third metal layer into an electrically insulating material, and then converting the third metal layer into an electrically insulating material.
Sequentially selecting predetermined portions of the second and first metal layers under different conditions from selectively converting the third metal layer into an electrical insulating material using the portion of the metal layer that is not converted into an electrically insulating material as a mask. This is a bag manufacturing method for semiconductor devices that converts it into an electrically insulating material. Since the step of selectively converting the laminated metal body into an electrically insulating material is performed in two steps, the shape in the machine direction can be made to a predetermined value. That is, first, the third metal layer is selectively oxidized into a predetermined shape including the lateral waviness of the insulating material. At this time, the second metal layer serves as a stopper. Then, since the second and first metal layers are converted under conditions that allow selective oxidation of these metal layers, the entire laminated metal body is eventually formed into a predetermined shape. Moreover, when selectively oxidizing the entire laminated metal body under the same conditions continuously, it takes a long time, and for this reason, if the same mask is used only on the third metal layer, the mask may deteriorate, and the cross-sectional It is also conceivable that the shape differs in the thickness direction. In this respect, in the present invention, the remaining portion of the third metal layer also acts as a mask, so that the selective oxidation of the second and first metal layers is reliably performed. Furthermore, it goes without saying that selective oxidation can be performed in two steps to control and modify the cross-sectional shape in the thickness direction by controlling the conditions. According to the invention, an extremely thin aluminum thin film layer (hereinafter referred to as the same) preferably provided to maintain good ohmic contact with the semiconductor, tantalum bonded thereon,
An electrode is constructed of a shielding film layer made of tungsten or molybdenum and a conductive film layer made of aluminum bonded thereon.

In such an electrode structure, ohmic contact between the electrode and the semiconductor is obtained by heating the semiconductor substrate to an appropriate temperature. At this time, the alloy temperature of silicon and aluminum is 575o
○, while the alloying temperature with tantalum, tungsten, or molybdenum is 2400 qo and 2150 qo, respectively.
, 187,000, which is extremely high temperature compared to aluminum, so by selecting the heating temperature of the silicon substrate near the alloy temperature of aluminum, only the aluminum thin film layer reacts with silicon to form metal silicide and obtain good ohmic contact. be able to. The depth of the metal silicide layer that is formed is determined by the heating temperature and the thickness of the aluminum film, so if you control the thickness of the aluminum film in advance according to the depth of the bond, it will work even after long heat treatment. Breakage of the joint can be reduced. For example, when making ohmic contact with an aluminum thin film by heating a silicon substrate to 400q0 to 50p0, if the depth of the shallowest junction in the silicon substrate is 0.2 to 0.8 microns, the aluminum thin film The layer thickness should be less than 0.01-0.05 microns, depending on the bond depth, so that the ohmic contact heat treatment and subsequent heat treatments (generally not exceeding 50,000 µm) will destroy the bond. can be prevented.

The tungsten or molybdenum layer on the thin aluminum film need only have a thickness that is effective as a barrier to the overlying aluminum conductive layer. When using the selective oxidation method described below, for example, 0.1
Around micron is convenient. As described above, by using the electrode structure of the present invention, excellent thermal/annual stability can be obtained even in the case of a semiconductor device having an extremely shallow degree. Furthermore, according to the present invention, since the selective oxidation method is used to form the electrode portions instead of the conventional selective etching method, the semiconductor surface is coated with an electrically and chemically safe metal oxide film at the same time as the electrodes are formed. completely covered with.

Therefore, the junction formed inside the semiconductor is protected from contamination from the outside, and high reliability can be obtained.
Next, in order to better understand the present invention, the present invention will be explained using figures.

Common parts in each figure are designated by the same reference numerals. Referring to FIGS. 1a-g, the preferred embodiment of the present invention is fabricated using a selective anodization process as described below. First, a semiconductor substrate 1 [the first
A thin aluminum film 3 with a thickness of 0.01 micron is uniformly deposited on the surface of Figure a], and then subsequently with a thickness of 0.1 micron.
A micron tantalum thin film 4 and a 1.5 micron thick aluminum film 5 are deposited [FIG. 1b]. Next, a first chemical conversion treatment is performed on the entire surface of the aluminum film 5 to form a porous alumina film 6 with a thickness of about 0.1 micron.
Figure c]. This porous alumina film 6 has the effect of increasing the adhesion of the photoresist in the next second chemical conversion treatment step.
To form the porous alumina film 6, it is appropriate to use a 10% aqueous chromic acid solution and perform constant voltage anodization at a forming voltage of 10 V for 10 minutes. Next, photoresist is applied to the surface of the porous alumina film 6, parts other than those that will become electrode wiring are covered with photoresist 12, and a second chemical conversion treatment is performed using the photoresist as a mask, so that the photoresist of the porous alumina film 6 adheres. A non-porous alumina film 7 is formed on the remaining portions (FIG. 1d). This second chemical conversion treatment uses a chemical solution in which ethylene glycol is saturated with ammonium lateral acid, and the chemical conversion voltage is 80V.
It is appropriate to carry out constant voltage conversion for 15 minutes. Next, after removing the photoresist, a third chemical conversion treatment is performed using the non-porous alumina film 7 as a mask to remove the parts other than the parts covered with the non-porous alumina film 7, that is, the parts covered only with the porous alumina film. The aluminum layer 5 is converted into a porous alumina 8 over its entire thickness (FIG. 1e). Third
For the chemical conversion treatment, it is preferable to use 10% dilute sulfuric acid and apply a chemical conversion voltage of 10 V to perform constant voltage chemical conversion. In this embodiment, the portions of the aluminum layer other than the portions masked by the nonporous alumina film 7 are converted into porous alumina by a chemical conversion treatment lasting about 15 minutes. Further, in this third chemical conversion treatment, the tartan thin film 4 is hardly chemically converted. this is,
Tartan oxide can only be made in a nonporous form, and it is thought that a chemical conversion solution that forms a porous oxide will not form a nonporous oxide. Next, a fourth chemical conversion treatment is performed to anodize the tartan thin film 4. At this time, the remaining aluminum waist portion covered with the non-porous alumina film 7 acts as a mask. 9 and alumina 10' are converted. [Figure 1 f
]. In the fourth chemical conversion treatment, a 3% aqueous solution of ammonium citrate is used as the chemical conversion liquid, and in this example, it is appropriate to perform constant voltage conversion at a conversion voltage of 20 for 15 minutes. Next, the semiconductor substrate is subjected to heat treatment at 450° C. for 1 hour. This heat treatment forms a good ohmic contact between the electrode portion and the semiconductor and at the same time chemically stabilizes the alumina and tantalum oxides formed by the anodization. Finally, a barrier portion 11 for attaching an external lead or an upper wiring layer is provided at a desired portion of the alumina film 7 covering the electrode wiring, thereby completing the formation of the electrode wiring (FIG. 1g). The semiconductor device formed by the manufacturing method shown in this embodiment has extremely high stability against heat treatment because the amount of aluminum that causes an alloy reaction with the silicon semiconductor is kept very precisely and to a small amount.

When a conventional aluminum electrode is applied to a silicon semiconductor device having a washed emitter structure with a junction depth of 0.3 microns, a heat treatment of 300 mm will take about 30 minutes.
At 40 pm, an emitter junction short circuit occurs in about 5 minutes, but in the embodiment of the present invention, it takes 2 hours at 40,000 pm, and 500 pm at 40,000 pm.
00 for 5 hours, but no damage was observed. As described above, the main part of the invention is to control the reaction temperature between a thin film layer of controlled thickness of a metal that forms a good ohmic contact with a semiconductor and a semiconductor deposited thereon. The process consists of stacking a thin metal film layer with an extremely high electrical conductivity and a metal film layer with good electrical conductivity, and then processing it into electrode wiring by applying an anodic oxidation method. The great effect of this invention is that it is possible to easily and reliably obtain a semiconductor device which has a thermally extremely stable electrode and whose semiconductor surface is completely protected by an electrochemically stable metal oxide coating.

Therefore, the technical scope of this invention is not limited to the above embodiments, and the rights of this invention extend to all devices shown in the claims.

[Brief explanation of the drawing]

1A to 1G are cross-sectional views of a semiconductor device at each step of a manufacturing method according to an embodiment of the present invention. In the figure, 1 is a silicon substrate, 2 is a silicon oxide film, 3 and 5 are aluminum films, 4 is a tantalum film, 6, 7, 8, and 10 are alumina, and 9 is tantalum oxide. hair figure

Claims (1)

[Claims] 1. A first metal layer is formed on a semiconductor substrate having a silicon oxide film on a predetermined surface, a second metal layer is formed on the first metal layer, and a third metal layer is formed on the second metal layer. When selectively converting a laminated metal layer body in which a metal layer is formed into an electrically insulating material, the second metal layer and the third metal layer have different conversion characteristics. The third metal layer was selectively converted into an electrically insulating material, and then the third metal layer was selectively converted into an electrically insulating material using a portion of the third metallic layer that was not converted into an electrically insulating material as a mask. 1. A method for manufacturing a semiconductor device, comprising sequentially and selectively converting predetermined portions of the second and first metal layers into an electrically insulating material under different conditions.